How to render a matte with Eevee?
If you've already set the World to 'Transparent' then you shouldn't need to disable the lamps or set the world to black - just use the Alpha channel of the output as your matte - it will be 1.0 wherever it hits an object and will be 0.0 wherever it does not. In Eevee, transparent objects will produce alpha of 1.0 (as transparency is only simulated in Eevee). 

For a faster render you could switch off unnecessary features (that don't affect the Alpha render) such as Screen Space Reflections, etc.